1. Field of the Invention
The present invention relates to mobile X-ray apparatus used in taking X-ray photographs of immovable patients in operating rooms or emergency treatment rooms of medical institutions, or in taking X-ray photographs on rounds, and more particularly to a steering mechanism for this type of apparatus.
2. Description of the Related Art
Conventionally, this type of apparatus has an X-ray tube, an X-ray tube control unit, a carriage driving control unit and so forth mounted on a power-driven carriage. An operator standing behind the carriage manipulates a steering control bar or bars to drive the carriage.
In one example of mechanisms for steering the carriage, a control bar secured to a main body of the apparatus has a portion thereof rotatable about its axis in the same way as the accelerator of a motorcycle is rotated. A direction of rotation is detected for driving the carriage forward or backward. An angle of rotation of the control bar is also detected and outputted as a moving speed signal to the driving control unit.
In another example, as disclosed in U.S. Pat. No. 4,697,661, a single control bar is supported by a main body of an apparatus such that opposite ends of the bar are displaceable. When an operator applies forces to the control bar, displacements of the opposite ends of the bar are detected. Respective displacement signals are outputted to a control unit as steering signals for controlling a pair of drive wheels of a carriage.
The conventional apparatus noted above have the following disadvantages:
The former provides an unnatural feeling of control since the rotation of the control bar is unlike the feeling of "push forward" or "pull backward". Besides, it is not simple or easy to provide the same control bar with means for outputting turnabout signals.
In the latter, the operator normally holds the opposite ends of the control bar with both hands to control the carriage. Since only one bar is provided, right and left operating forces and amounts of displacement influence one another to provide an unnatural feeling of control. When the operator pushes only the left end of the control bar, for example, the right end of the control bar will also be displaced slightly. As a result, not only the left drive wheel but the right drive wheel will also make a slight movement. Thus, an actual movement of the carriage deviates from the feeling of control.